(a) Technical Field
The present disclosure relates generally to vehicular safety, and more particularly, to a steering column system for enhanced vehicle occupant safety.
(b) Background Art
Crash tests are a form of destructive testing usually performed in order to ensure safe design standards for various modes of transportation including, primarily, vehicles. There are different types of crash testing—administered in the United States by the National Highway Transportation Safety Administration (NHTSA)—for evaluating different aspects of a vehicle's crashworthiness. The most traditional crash test is known as a “frontal-impact crash test,” whereby a vehicle is driven to collide head-on with a barrier, such as a concrete wall. FIG. 1A illustrates an example frontal-impact crash test, in which the angle of impact directly opposes the direction in which the vehicle 100 travels. In this case, a load generated by colliding with the barrier 110 is experienced throughout the entire front end of the vehicle 100. Meanwhile, in “overlap crash tests,” only part of the front end of a vehicle impacts a barrier. The impact force remains approximately the same as in a frontal-impact test, but a smaller fraction of the vehicle is required to absorb the force.
Recently, the NHTSA proposed a new “oblique frontal crash test,” where a vehicle is struck by a barrier (e.g., a Research Movable Deformable Barrier (RMDB)) at an angle that is offset from the direction in which the vehicle travels.
Notably, in oblique frontal collisions, where the primary loading is not experienced throughout the entire front end of the vehicle, the lateral acceleration of the collision will cause an occupant (e.g., driver, passenger, etc.) to move toward the Principal Direction of Force (PDOF), causing both forward and lateral motion of the driver, as shown in FIG. 2. If the PDOF is far enough off-center, an occupant may load the traditional frontal restraints (e.g., airbag system) in a manner not represented in current regulatory testing. Indeed, recent oblique collision testing has shown that a primary frontal airbag system alone has failed to adequately protect a driver where kinematics of the driver have significant lateral input, propelling the driver between the conventional driver-side airbag, and causing the driver to strike the dash panel in an unsafe manner. Thus, traditional frontal restraints may not provide a sufficient level of protection for the occupant in the event of an oblique frontal collision, as they would if loaded in a more traditional regulatory loading condition, such as a head-on collision.
Some vehicles may be equipped with a curtain airbag (CAB) to provide additional protection to the head and/or upper body of the driver in frontal impacts with significant lateral input. The CAB typically inflates from the front of the driver-side door rearwardly to the rear passenger door. In order for the CAB to provide adequate head protection in the oblique impact shown in FIG. 1B, the bag must be made to be wider, longer, or with some tethering to create a “pocket” for restraining the upper torso. However, these CAB designs are limited by inflation pressures, timing, and packaging concerns due to the addition of extra material.
Other shortcomings in conventional vehicle protection systems exist, such as airbag inflators which often use a pyrotechnic solid (e.g., sodium azide). However, the resultant gas has a high temperature, and as it exits the airbag through the vents formed therein, it may cause a burn hazard to the passenger's hands. Further, conventional energy-absorbing mechanisms in steering columns for absorbing energy during a collision event typically employ bending, elongation, or tearing of metal. However, due to variations in metal chemistry, processing, and geometry, these mechanisms are often vulnerable to performance variations, including the potential for interruptions to smooth load transfer. Off-axis loading of the steering column can result in interference with the resultant sliding motion of the steering column, which is necessary for safely handling loads caused by a collision.